40 The Middle Devonian Deposits of Maryland 



others of equivalent value which shall obviate the duplication and con- 

 fusion Avith which we are now embarrassed." * In accordance with this 

 statement the paper contained a series of names for the periods or groups 

 of the New York series which, were derived mostly from characteristic 

 localities in New York state, and the hope was expressed that thus would 

 be preserved " under the necessity of change, the eminent title of New 

 York state to its full and ancient representation in the classification of 

 the Paleozoic deposits and time." In place of the Hamilton period of 

 Dana composed of the Marcellus shale and Hamilton stage, Erian was 

 proposed with the intention of saving the term " Erie division " of the 

 New York geologists, which included all the formations from the base 

 of the Marcellus shales to the top of the Chemung, " to the New York 

 nomenclature by reviving it Avith a restricted meaning." ' 



Adoption op Komney Formation 



In connection with the preparation of the maps and text for the 

 folios of the Geologic Atlas of the United States, the United States 

 Geological Survey carefully considered the subjects of geological cartog- 

 raphy and nomenclature. In the Tenth Annual Eeport the Director gave 

 a lengthy account of a conference of a number of geologists connected 

 with the United States Geological Survey held in 1889 at which it was 

 decided that there should be recognized for the clastic rocks both struc- 

 tural and time divisions, and that the structural divisions should be con- 

 sidered the imits of cartography and called formations. In the definition 

 of a formation it was stated that " As each lithologic unit is the result 

 of conditions of deposition that were local as well as temporary, it is to 

 be assumed that each formation is limited in horizontal extent; the 

 formation should be recognized and should be called by the same name 

 as far as it can be traced and identified by means of its lithologic char- 

 acters, aided by its stratigraphic association and its contained fossils." ^ 



In 1903, these rules were revised by the United States Geological Survey 

 and the revision published the following year in the Twenty-fourth An- 



' Science, N. S., Vol. X, p. 875. 



' Ibid., p. 877. 



" 10th An. Kept. U. S. Geol. Surv., 1890, p. 64. 



I 



